SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

STAFF REPORT CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY SAN JOAQUIN COUNTY This report was developed as an informational item to the Board regarding the status and permitting issues associated with renewing the NPDES Permit for the Stockton Regional Wastewater Control Facility (RWCF), San Joaquin County. BACKGROUND The RWCF is owned and operated by the City of Stockton. The RWCF is located immediately west-southwest of the City of Stockton. The secondary facility has a design flow of 42 mgd and the tertiary plant has a design flow of 55 mgd. On average the RWCF treats approximately 34 mgd yearly. The facility treats domestic and industrial wastes servicing a population of roughly 283,000. The RWCF accepts wastewater from approximately 32 significant industrial users, which amounts to 5.3 mgd or approximately 16 % of the facility's yearly average flow. The RWCF provides wastewater treatment consisting of screening and grit removal,primary sedimentation, followed by high rate trickling filters and intermediate settling basins. Additional treatment is obtained by piping the wastewater under the San Joaquin River to oxidation ponds, followed by dissolved air flotation (DAF), mixed-media filters and chlorination/dechlorination facilities. The DAF and filters are operated July through October during peak algal production periods. Wastewater is discharged to the San Joaquin River upstream of the Stockton Deep Water Channel. The beneficial uses of water within the San Joaquin River and Sacramento-San Joaquin Delta included municipal and domestic, industrial, and agricultural supply; water contact and non-contact recreation; aesthetic enjoyment; navigation; and, preservation and enhancement of fish, wildlife, and other aquatic resources. EXISTING NPDES PERMIT The Regional Board adopted the existing NPDES permit No. CA0079138, Order No. 94-324, 28 October 1994. The Order found that more stringent BOD and ammonia effluent limitations were needed to protect the receiving waters. Seasonal effluent limitations for CBOD and ammonia were included in the Order to aid in the attainment of receiving water dissolved oxygen (DO) objectives. The Basin Plan requires a DO concentration of 5.0 mg/l within the San Joaquin River, while the Salinity Plan requires a DO concentration of 6.0 mg/l within the San Joaquin River inside the reach of Turner Cut to Stockton from 1 September through 30 November. In addition to more stringent effluent limitations,the Order also included provisions to perform a mercury study, perform a risk assessment evaluation of the disinfection process effectiveness, provide a Thermal Plan compliance evaluation/study, and provide a mineralization minimization plan. The provisions for the mercury study and the health risk assessment also allowed for the permit to be reopened and additional limitations applied if information from the studies suggested action was required. Staff